The present invention relates to a side-by-side wellhead system which may be used to drill and complete a number of hydrocarbon wells. More particularly, the present invention relates to a side-by-side wellhead system which comprises one or more high strength, low profile connectors to secure the wellhead housing component of the system to certain other components, such as a drilling riser or a christmas tree.
Prior art side-by-side (SXS) wellhead systems are commonly used to drill and complete a number of hydrocarbon wells from within a single conductor housing. As shown in FIG. 5, such a wellhead system may comprise a base plate 74 which is welded to the top of a conductor housing 70, two casing strings 76a and 76b which are each suspended from the base plate, and a landing support ring 72 which is bolted to the top of the base plate. In this example, the well on the right hand side of FIG. 5 is covered by an abandonment cap 78, which is connected to the top of the landing support ring 72 with a bolted flange connection that comprises a number of bolts 80. In addition, a wellhead housing 60 is installed in the well on the left hand side of FIG. 5 and is connected to the landing support ring 72 using a bolted flange connection which includes a number of bolts 66, only one of which is shown. Furthermore, in the drilling mode of operation of the SXS wellhead system shown in FIG. 5, a drilling riser 62 is connected to the top of the wellhead housing 60 via a bolted flange connection which comprises plurality of bolts 64, only one of which is shown.
The bolted flange connections which are used to connect the various components of prior art SXS wellhead systems are time consuming to install and remove. In addition, the offset loading inherent in SXS wellhead systems limits the maximum operating pressures such bolted flange connections can safely withstand. Furthermore, the flanges themselves occupy a substantial portion of the available cross-sectional area of the wellhead housing, thus reducing the maximum diameter of well casing which can be used in the SXS wellhead system.
These and other limitations in the prior art are addressed by providing a wellhead system for use in completing at least two well bores from within a single conductor housing. The wellhead system comprises at least one wellhead housing which is supported on the conductor housing and which comprises a top portion that is adapted to be connected to a lower portion of a wellhead component, a casing hanger which is supported within the wellhead housing and from which a casing string is suspended, and a connector for securing the wellhead component to the wellhead housing. In accordance with the present invention, the connector is selected from the group consisting of a latch ring and a segmented clamp assembly.
In one embodiment of the invention, the wellhead component comprises a christmas tree which includes a lower connection portion that is received within the top portion of the wellhead housing and the connector comprises a radially expandable latch ring which is disposed between the lower connection portion and the wellhead housing. In addition, the latch ring is supported on the lower connection portion and is expandable into a groove which is formed on the wellhead housing to thereby secure the christmas tree to the wellhead housing.
In another embodiment of the invention, the wellhead component comprises a drilling riser and the connector comprises a segmented clamp assembly which is secured around the wellhead housing and the drilling riser. In addition, the segmented clamp assembly extends around the wellhead housing and the drilling riser an angle of less than 360xc2x0. Furthermore, where the wellhead system comprises three wellhead housings, the segmented clamp assembly extends around the wellhead housing and the drilling riser an angle of approximately 225xc2x0. Moreover, the segmented clamp assembly is preferably supported on the drilling riser prior to being engaged with the wellhead housing.
Thus, the SXS wellhead system of the present invention uses a segmented clamp assembly during the drilling mode of operation, and an internally latching connector during the completion and/or temporary abandonment mode of operation. These types of connectors offer several advantages over the bolted flange connections used on existing SXS systems. Both the segmented clamp assembly and the internally latching connector allow for greater operating pressures within the system because they are able to withstand greater bending moments than the bolted flange connections used on existing SXS systems. In addition, the reduced profile of the internally latching connector allows for larger casing strings to be suspending in a given wellhead housing. Furthermore, the use of an internally latching connector in the production mode of operation provides a cost effective method for connecting the tree to the wellhead housing, since there is no need to leave a permanent segmented connector on the wellhead housing.
These and other objects and advantages of the present invention will be made apparent from the following detailed description, with reference to the accompanying drawings.